There is a clear demand for the monitoring of air-borne compounds that may have health effects on exposed individuals. A great interest exists for compounds that have occupational exposure limit values, set by governmental bodies, to ensure that the levels of such compounds are satisfactory low. In many cases it is not known what the air contaminants consist, of and for this reason it is of interest to learn more details about the nature of these “unknown” compounds and to reveal the identity of the most predominate ones. Another field of interest is to study and check the effect of measures with a view to reducing these levels in air, e.g. to check the “true” ventilation efficiency or other measures to control the air levels. Devices for this purpose can also be used for the monitoring of the quality of compressed air and air in respiratory protective devices. Other fields of application for such devices are e.g. the control of different volatile compounds present in food. Such compounds can be used as markers for degradation of certain food components or to monitor raw materials to ensure a satisfactory quality. Such devices may also be used to ensure that other compounds not have contaminated food. In hospitals such devices can be used to check the air levels of e.g. narcosis gases and to ensure that the personnel, patients and others are not exposed to toxic levels. Chemical warfare agents are also compounds that need to be checked for in order to reveal the presence thereof and to ensure that individuals are not exposed.
In environmental analysis there is a need to monitor the quality of air in cities, public places and in the nature. One purpose is to obtain background data for statistical studies and to check if the levels are below the levels set by national and international bodies. Such devices can also be used to check if the emission of industrial pollutants results in exposure in the nature or in populated areas. The achieved data can have an impact on decisions and interpretation of a certain situation. There is therefore a demand of a satisfactory high quality of the data.
There are many examples of air pollutants that occur in both gas and particle phase. Of special interest are the size fractions that have the ability to reach the lower respiratory tract. There are reasons to believe that the toxicology is different depending on not only the chemistry as such but also on the distribution on different target organs in the body of humans. There is a need to know more about the exposure to the respirable particle fraction present in air.
Numerous devices exist for the monitoring of air-borne compounds and there is a great variety of technology used. In principle, the devices can be grouped in selective and non-selective devices. Non-selective devices give a response for several compounds and do not differentiate between two or several compounds and may also result in false positive results. Such devices are today still used, possibly due to the low cost. In many applications, false positive results can give rise to a high cost for the user, if costly measures are performed from invalid data.
Selective devices give a certain response for a selected compound or a group of compounds. Other present compounds do not interfere with the result. The frequency of false positive results will be much less as compared to non-selective monitoring. The quality of the data obtained is essential. Typical factors that describe the quality of the data are: repeatability, reproducibility, linearity (calibration graph characteristics with intercept and background), detection limit and quantification limit. In addition, knowledge regarding the interference from other compounds is necessary. It needs to be mentioned that a certain compound can influence the result even if the compound does not itself give rise to a response.
Similar techniques for the detection of air-borne compounds involves the use of e.g. photo ionisation detectors (PID, Thermo Scientific, Franklin, Mass., USA), flame ionisation detectors (FID, Thermo Scientific, Franklin, Mass., USA), infrared detectors (IR), portable gas chromatography (GC)-PID (PID Analyzers, Pembroke Mass., USA), portable GC-mass spectrometers (MS, Inficon Inc., New York, USA), GC-DMS ((Differential Mobility Spectrometry), Sionex Inc., Bedford, Mass., USA). All techniques give a response for a certain analyte, but to know the concentration the response needs to be translated into concentration by using information from a more or less sophisticated calibration curve. For many of the above techniques, the response varies with time due to ageing, contamination of the detector (reduces the signal) and other variables.
The GC-DMS technique mentioned above is used in the MicroAnalyser instrument (Sionex Inc., Bedford, Mass., USA). The GC-DMS technique is based on GC separation, with regards to compound volatility, in combination with the separation in a DMS sensor, with regards to other molecular properties such as size shape, charge etc.
There are several drawbacks with the present types of instruments. For PID and FID, identification of the individual chemicals is not possible. PID and FID detectors measure the sum of VOC (Volatile Organic Compounds). Infrared detectors suffer from problems with inferences. IR detectors are not possible to use when monitoring VOCs at low concentration when other interfering compounds are present.
Polyurethane (PUR) products as air pollutants are of particular interest to monitor and analyze. They frequently occur in industry, in particular in manufacturing and handling polyurethane foam, elastomers, adhesives and lacquers. Polyurethane is produced by the reaction of a bifunctional isocyanate with a polyfunctional alcohol. The satisfactory technical qualities of polyurethane have resulted in a large increase of its use and application fields during the last decades. In connection with thermal decomposition of polyurethanes, however, the formation of isocyanates, aminoisocyanates, anhydrides, and amines might occur, and extremely high contents can be found in air, e.g. when welding automobile sheet steel. Besides the known types of isocyanate, also new types of aliphatic isocyanates have been detected, in connection with e.g. heat treatment of car paint. Most of the isocyanates formed have been found to be represented by so-called low-molecular isocyanates. During short periods of time (peak exposure) particularly high isocyanate contents can be present, as is the case, for instance, when welding. Of all the dangerous substances on the limit value list, isocyanates have the lowest permissible contents. Exposure to this new type of isocyanates was previously unheard of. Isocyanates in both gas and particle phase have been detected in connection with welding, grinding and cutting of painted automobile sheet steel, and respirable particles in high contents containing isocyanates have been detected. In thermal decomposiion products of painted automobile sheet steel, detection has been made of, among other things, methyl isocyanate (MIC), ethyl isocyanate (EIC), propyl isocyanate (PIC), phenyl isocyanate (Phi), 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,4- and 2,6-diisocyanate toluene (TDI) and 4,4-methylene diphenyldiisocyanate (MDI).
In thermal decomposition of phenol/formaldehyde/urea-(FFU)-plastic, isocyanic acid and methyl isocyanate are formed. FFU plastic is used, among other things, in wood glue and as a binder in mineral wool (and bakelite), which is frequently used as insulation for ovens and furnaces in industrial and domestic use. New fields of application in which exposure to isocyanates has been detected are the soldering and processing of printed circuit boards in the electronic industry, the welding, grinding and cutting of painted sheet steel in the automobile industry and the welding of lacquered copper pipes. Isocyanates have a varying degree of toxicity to the organism depending on their chemical and physical form. As a result, the hygienic limit values have been set at an extremely low level in all countries. For the exposed individual, the degree of exposure to isocyanates varies considerably in different operations during a working day and in connection with breakdowns. Thermal decomposition products from PUR constitute a special problem, since new and completely unknown isocyanates are formed, whose toxicity has not yet been analyzed in a satisfactory manner. Furthermore, the increasingly sophisticated measuring methods have revealed exposure to isocyanates in an increasing number of operations in industry.
To sum up, there are a number of operations in numerous working areas where people are daily exposed to or at risk being exposed to isocyanates at a varying degree. Considering the ominous tendency of isocyanates to cause respiratory diseases and the fact that there are some carcinogenic substances among the thermal decomposition products of polyurethane, e.g. 2,4-diamine toluene (TDA), 4,4-methylenediamine (MDA) and MOCA, it is very important to measure in a reliable, sensitive and rapid manner any presence of isocyanates, but also other decomposition products dangerous to health, in environments where there is such a risk.
There is also a particular interest to monitor and analyze such solid/liquid air pollutants as asbestos, dust, metals, bacteria, oil mist, and fungi.
There is also a need to monitor and analyse certain chemical substances present in liquids, e.g. drinking-water, and flows in connection with purification plants. In such cases the liquid flow is transported through a sampling device in which the chemical to analyze is adhered to a specific reagent immobilized within the sampling device, e.g. in a filter and/or on the inner walls thereof.
A sampling device for analysis of air pollutants, more precisely poluretane products, is disclosed in WO 00/75622, and further developments thereof are disclosed in WO 2011/108981 and in WO 2007/129965. The sampling devices, also called samplers, disclosed in these publications collect the probed chemical in a two-step process. A fluid in which the amount of a chemical is to be measured is pumped through the sampling device using a controlled flow. The chemical substance of interest present in the gas phase of the fluid is collected in an adsorption tube using a regent coated on the surfaces present inside the tube. The flow of fluid is further pumped from the adsorption tube to and through a filter impregnated with the same reagent. The chemical substance in solid form or adhered to particles in the fluid is collected in the filter. After the measurements have been performed, the sampling device is sealed and is shipped to a laboratory for analysis of the amounts of chemical substance collected during the measurements.
However, it is very important that the sealing of the filter of the sampler is fluid-tight and secure for the measurement to be reliable. If leakage occurs during the measurement in such a way that the gas flow may circumvent the filter, the measurement will be inaccurate. Currently used samplers show some structural drawbacks. E.g. the filter is held in place by a filter holder and is in contact directly with an abutment portion of the filter holder. By rotating either the filter holder or the adsorption tube, or both, when assembling the sampler components, the filter may be sheared or broken due to the rotational forces induced, and leaks may occur. The filter may also unintentionally shift in position during the rotation of the sampler components creating large gaps around the filter, thereby making the measurement inaccurate.
A further problem is that when storing the assembled sampler, the pressure exerted on the filter may alter due to ageing of the filter. Thereby the sealing properties may be negatively affected.
Before and after a sampling session has been performed it is also important that the sampling device is protected from the outside environment with a view to avoiding contamination via diffusion of undesired substances into the sampler. Therefore, it is important to use sealing caps in the inlet and outlet ends, in particular in the inlet end of the sampler when the sampler not is in use, e.g. during transport. Otherwise, the measurements may be negatively affected and destroyed by the undesired diffusion into the sampler. Thus, as sampling in several environments may be very expensive and require highly accurate measurement results, it is of great importance that the sampler is fluid-tight against the outside environment when assembled, in particular during handling and transport before and after the measurements. Traditionally, interior caps of plug type have been used since they are simple, air-tight and robust. Interior caps need interior wall surfaces on the adsorption tube to abut to with a view to being able to create a fluid-tight sealing. However, on these inner wall surfaces adsorbed substances that are intended to be analyzed will stick to the surface of the cap and will then be excluded from the analysis when the cap is taken off at the analysis laboratory.
A further problem in connection with the use of caps is that when they are removed and placed nearby the sampler during the measurements, they may adsorb substances on their surfaces. When the caps are attached to the sampling device, the substances adsorbed on the surface of the inlet cap which is in contact with the interior of the sampling device may be desorbed and then instead be adsorbed in the adsorption tube, thereby disturbing the measurement result. Correspondingly, substances adsorbed in the surface of the outlet cap which is in contact with the interior of the sampling device may be desorbed and instead then be adsorbed on the bottom surface of the filter, thereby also disturbing the measurement results. Caps that are removed and placed nearby the sampler during measurements may also be lost, and it may also take time to find them after a finished measurement, allowing time for undesired diffusion into the adsorption device. The latter is especially a problem in rough conditions, e.g. at measurements in cold places, where gloves are used, or at sea, where waves may make practical chores harder.
There is also a problem in connection with the use of sampling devices made by a standard polymer material or other no anti-static material in that air sampling through a non-conductive sampling device can create an electrical static charge to develop on the surfaces of the sampling device. The static charge will attract the particles of interest to collect onto the wall(s) of the sampling device instead of being collected by the filter medium contained in the air sampling device that was designed to retain the particles of interest. When the filter medium is removed from the sampling device with a view to being analyzed, the particles of interest remain attached to the electrostatically charged device. This creates incomplete recovery of the sample, since particles of interest are left behind in the sampling device, and these wouldn't be analyzed. This problem creates an inaccurate concentration determination from the collected air sample.
The rate at which the electrostatic charge is created is highly variable, with variables being the following: the relative humidity of the air being sampled (as the relative humidity decrease, the electrostatic charge increases). The amount of the electrical charge of the particle itself will vary. The charge can be created depending on how the particle(s) becomes air-borne, and how long the particle(s) has been suspended in air. The speed at which the particles enter the sampling device can affect the electrical static charge that is buildt up on the surfaces of the sampling device.
Another problem in connection with use of sampling devices for the measurement of air-borne compounds in a fluid flow is the risk that the sampling device is tampered or manipulated during handling thereof, i.e. during the period from when it is transported from the supplier or the analysis laboratory to the user, is subjected to the sampling step by the user, and then is transported from the user to the analysis laboratory. When the sampling device is sent from the supplier or the analysis laboratory to the user, the filter is located within the sampling device, fluid tightly secured between the adsorption device and the filter holder. During the sampling step and the subsequent transport of the sampling device to the analysis laboratory the filter must be located within the sampling device all the time, i.e. the adsorption device and the filter holder may not be separated from each other. However, it has turned out that sampling devices have been manipulated or tampered with during the transports or by the user before, during, and after the sampling step, either unintentionally or intentionally. E.g., it has happened that the adsorption device has been separated from the filter holder during the transport of the sampling device to and from the user or by the user at the sampling site. In such a case the filter becomes exposed to air-borne components from other sites than the sampling sites and also during indefinite time periods. This of course leads to false or inaccurate analysis results in the end. The reason for such a manipulation could be that it is made by mistake or with a view to intentionally provide a different analysis result than the correct one. It has also happened that the filter has been exchanged with another filter containing the intended analyte components, i.e. reaction products, in intentionally wrong concentrations or having other compounds bound thereto.
Another problem is that when the sampling device has been used once it is further used one or more times after the analysis step of the laboratory. E.g., when the adsorption device has been separated from the filter holder and the filter has been taken out for analysis, it has happened, unintentionally or intentionally, that a new filter has been introduced in the filter holder and that the adsorption device thereafter has been connected to the filter holder, thereby creating a sampling device for repeated use. When such a sampling device is sent to a user for sampling, the interior surfaces thereof normally are contaminated with different compounds from the previous sampling, and the analysis results finally obtained at the analysis laboratory will be false or inaccurate. Such a manipulation can be made by mistake, e.g. when the different parts of the sampling device appear to be unused, or, in the intentional case, with a view to saving money by reuse thereof. U.S. Pat. No. 5,601,711 discloses a filter device for separation of materials, wherein it comprises two or more inline tubular elements, one or more of which is a module that houses a filter medium. The elements may have complementary connection structures, e.g. an o-ring, compression connections, bayonet connections, snap connections, and the like.
US 2010/0010455 discloses a medical delivery system adapted to be locked axially and unlocked rotationally.
US 2009/0242470 discloses a filter closure system having a connecting end and a connecting head which have a bayonet connection with receiving slots or receiving projections and matching insertion projections.
Thus, there is a clear need to provide an improved sampler containing a filter that is fluid-tightly sealed without risk of any leakage around the edges of the filter. Further, there is a need for an improved sampler with a view to avoiding contamination from its surroundings during handling and transport of the sampling device and for a sampler having caps that are not lost during measurement and that not may contaminate the sampling device by the surroundings.
Thus, there is also a need for a way to prevent manipulation and tampering of the sampling device during the transport from the supplier or sampling laboratory to the user, by the user in connection with the sampling step, and during the transport from the user to the analysis laboratory. There is also a need to prevent use of the sampling device more than once.